1. Field of the Invention
Two-way data communication system utilizing optical isolating circuitry.
2. Description of the Prior Art
A number of systems exist wherein apparatus at a central location interrogates apparatus at remote locations with the subsequent transmission of data from these remote locations back to the central location.
For example, in a nuclear power generating complex, hundreds of remote stations may be located throughout the complex for gathering, by means of sensors, data relative to radiation levels, pressures, temperatures, and wind and fluid flows, to name a few. Each of the remote stations includes a computer means for handling the data and for transmitting such data back to a central control room for display and interpretation.
Any communications link between a remote station and the central station must be simple, reliable, and must allow for ground potential differences between the stations. To this end, use is made of optical isolating circuits, or opto-isolators to allow for not only ground potential differences but to provide high noise immunity. The technique utilized includes two cables for each separate link with a remote station, with each cable including a shielded pair of lines with one cable being for interrogation of a remote station and the other cable being for the transmission of data from that remote station to the central control.
It would be desirable to minimize the cable requirements for such installation without degrading performance. The present invention accomplishes these objectives.